Zeolitic materials, both natural and synthetic, have been demonstrated in the past to have utility as adsorbent materials and to have catalytic properties for various types of hydrocarbon conversion reactions. Certain zeolitic materials are ordered, porous crystalline metallosilicates having a definite crystalline structure as determined by X-ray diffraction, within which there are a large number of smaller cavities which may be interconnected by a number of still smaller channels or pores. These cavities and pores are uniform in size within a specific zeolitic material. Since the dimensions of these pores are such as to accept for adsorption molecules of certain dimensions while rejecting those of larger dimensions, these materials have come to be known as “molecular sieves” and are utilized in a variety of ways to take advantage of these properties.
Such molecular sieves, both natural and synthetic, include a wide variety of positive ion-containing crystalline silicates and substituted silicates, in which the silicon is partially or completely replaced by other tetravalent elements. These silicates can be described as a rigid three-dimensional framework of SiO4 tetrahedra and optionally tetrahedra of a trivalent element oxide, e.g., AlO4, in which the tetrahedra are cross-linked by the sharing of oxygen atoms whereby the ratio of the total trivalent element and silicon atoms to oxygen atoms is 1:2. The electrovalence of the tetrahedra containing the trivalent element is balanced by the inclusion in the crystal of a cation, for example an alkali metal or an alkaline earth metal cation. This can be expressed wherein the ratio of the trivalent element, e.g., aluminum, to the number of various cations, such as Ca/2, Sr/2, Na, K or Li, is equal to unity. One type of cation may be exchanged either entirely or partially with another type of cation utilizing ion exchange techniques in a conventional manner. By means of such cation exchange, it has been possible to vary the properties of a given silicate by suitable selection of the cation.
Prior art techniques have resulted in the formation of a great variety of synthetic zeolites. Many of these zeolites have come to be designated by letter or other convenient symbols, as illustrated by zeolite A (U.S. Pat. No. 2,882,243); zeolite X (U.S. Pat. No. 2,882,244); zeolite Y (U.S. Pat. No. 3,130,007); zeolite ZK-5 (U.S. Pat. No. 3,247,195); zeolite ZK-4 (U.S. Pat. No. 3,314,752); zeolite ZSM-5 (U.S. Pat. No. 3,702,886); zeolite ZSM-11(U.S. Pat. No. 3,709,979); zeolite ZSM-12 (U.S. Pat. No. 3,832,449), zeolite ZSM-20 (U.S. Pat. No. 3,972,983); ZSM-35 (U.S. Pat. No. 4,016,245); zeolite ZSM-23 (U.S. Pat. No. 4,076,842); zeolite MCM-22 (U.S. Pat. No. 4,954,325); and zeolite MCM-35 (U.S. Pat. No. 4,981,663), to name merely a few.
The general method of zeolite synthesis involves dissolving a source of a trivalent metal oxide, such as alumina, into an aqueous solution of sodium or potassium hydroxide. A source of silica or other tetravalent element oxide in the form of an aqueous slurry is then added to the solution, often together with an organic template, and the resulting gel stirred until homogenous. The gel is then transferred to a reaction autoclave and aged at temperatures of between 50° C. and 250° C. for time periods ranging from hours to days, depending on the zeolite required. The initial reaction gel composition has little resemblance to the chemical stoichiometry of the final zeolite product. In addition, the reaction gel is rich in sodium or potassium hydroxide depending on which final zeolite product is required.
For example, U.S. Pat. No. 4,956,166 discloses a process for the preparation of zeolite L, in which an alkaline reaction mixture comprising water, a source of alkali metal M1, preferably potassium, a source of silicon and a source of aluminum is heated to a temperature of at least 75° C. to form the zeolite L, characterized in that the reaction mixture comprises a source of copper and has a composition falling within the following molar ratios (expressed as oxides):
(M12O + CuO)/SiO20.18-0.36H2O/(M12O + CuO)25-90SiO2/Al2O3 5-15M12O/(M12O + CuO)  0.900-0.9999.
According to the present invention a novel molecular sieve material, designated EMM-7, has now been synthesized in an aqueous reaction mixture containing potassium hydroxide and in the absence of an organic directing agent. Based on measurements of its porosity and acid activity, EMM-7 has utility as an adsorbent and/or a catalyst for organic conversion reactions.